Dowel



Oct. 3, 1939. H. c. GRAHAM DOWEL Filed Oct. 1, 1938 6 m m mam /s Patented Oct. 3, 1939 UNITED STATES PATENT OFFICE Application October 1,

5 Claims.

This invention relates to dowels adapted to be sunk into timber, and consists in refinements of shape, in consequence of which the field of utility of such dowels is enlarged. The application is a continuation in part of an application filed by me Januaryz'l, 1938, Serial No. 187,203.

The invention is illustrated in the accompanying drawing. Fig. I is a view in side elevation of a dowel in which the invention is embodied. Fig. II is a view to larger scale, showing the dowel in end elevation. Figs. III and IV are fragmentary views, corresponding to Fig. I, that illustrate modifications in details of structure. Fig. V is a view corresponding to Fig. I illustrating a further modification; and Figs. VI and VII are views in cross-section, on the planes indicated at VIVI and VIIVII, Fig. V.

In Letters Patent of the United States, No. 2,014,892, granted Sept-ember 17, 1935, on the joint application of myself and Wiliiam B. Peirce, a dowel for the re-enforcement of timber, and typically of a railway tie, is shown and de scribed. The dowel of that patent is described to be a rod that is ridged, and the ridges extend in spiraled form. The lead of the spiraled ridges is such that, unlike an ordinary screw, the dowel may be driven into timber by a sledge; it will rotate as it is being driven; and when driven into sound timber it will be secure against retraction. Such a spiraled ridge may in a dowel that is half an inch in over-all diameter make one complete turn in a length of two inches or more, measured on the axis of the dowel.

My present invention consists in a refinement in the shape of such a dowel, in consequence of which it may be better adapted to particular uses; and the refinement of shape to which I allude is a localized reduction in over-all diameter. The dowel shown and described in the patent named is of uniform shape and size in cross-section, from end to end of its spindle-lke body; and, as has been said, the spiraled ridges formed upon it make complete turns in uniform intervals throughout its length. In the dowel I of Fig. I of the drawing that forms part of this application, while the spiraled ridges make complete turnsin uniform intervals from end to end, the over-all diameter is, throughout a medial portion a of the body, less than throughout the terminal portions b and c. In consequence,

the security of the dowel when sunk in timber (for example) throughout the extent of its spindle-like body, though far exceeding the security of a smooth and cylindrical dowel, is so far diminished from that of the dowel of the Graham 1938, Serial No. 232,765

and Peirce patent named, that it may be withdrawn. Accordingly, the dowel of Fig. I is shown to be provided with an integral head I I, by which withdrawal may be effected. The change in over-all diameter may be a change in height 5 merely of the outstanding spiraled ridges; and the change will not be abrupt. There will be a gradual diminution in the height of the ridges from the portion 0 to the portion a, and a gradual increase from the portion a, to the portion b. The dowel stands contrasted to a bolt whose shank elsewhere smooth is, throughout a portion of its extent, screw-threaded, both in the vastly different lead, that makes rotation possible under the drive of a sledge, and in the gradual increase in the height of the spiraled ridge-a feature that also contributes to the spiraled progress of the dowel into a timber or like body. It remains to say only this: that in withdrawal the instrumentalities must be such as to allow the .dowel to turn as it is withdrawn. Given this added characteristic, that it may be Withdrawn under tension, achieved with some diminution of security, the dowel becomes useful, for example, for uniting to an underlying timber a second wooden member that, exposed to wear, is less durable than the timber to which it is united and with respect to which there must in course of time be replacement of the second member.

In Fig. II the dotted circle m indicates the cylindrical surface to which the crests of the ridges coincide throughout the portion a of the shank of the dowel as illustrated in Fig. 1. Since the intervals are uniform through which the ridges make complete turns upon the shank, the angle at which the line of the crest extends with respect to the transverse plane is steeper in the portion a where the crests are lower than in the helical pitch of the portions 11- and c where the crests are higher. These crests of steeper pitch but lower elevation extend, however, with in the grooves sunkin the wood by the higher ridges of the leading portion c of the dowel.

In the driving of the dowel into wood, for example, it is the ridges of the portion 0 that spread 45 the fibres of the wood and that shape the matrix, so to say, in which the driven-home dowel lies. The ridges of the portions or and b follow in the already opened space; and, when the dowel is driven home, the ridges of the portion b lie precisely within and completely fill the grooves of the space opened by the portion 0. The dowel is snugly and tightly bedded in the wood, and no space remains for the ingress of moisture.

In Fig. III the diminution in over-all diameter, 55

the diminution in the height of the ridge, is resorted to, not only in the medial portion of the shank, but also in a terminal portion d between the portion 0 and the pointed tip of the dowel. The dowel is in any case advantageously provided with a conical or pyramidal tip l2, that is serviceable in directing the dowel in application to solid timber; and the additional feature, of spiraled ridges that spring from the base of the tip and increase gradually in height from zero to the maximum desired, is a feature that is further serviceable in directing the dowel to place.

The dowel of Fig. IV has all the features that have been described with reference to Figs. I and III, and the additional feature that a smooth, cylindrical body portion 13 is provided, into which at one end the spiraled ridges merge, and with which at the other end the tip at its base is continuous.

Actual dimensions may vary widely. By way of illustration, if the over-all diameter of the body of the dowel be elsewhere half a inch, and the interval within which the turn of the spiraled ridges is completed be something more than two inches, a diminution in over-all diameter throughout the medial portion a, by as much as one thirty-second of an inch will be adequate to afford the advantages and to render attainable such larger utilities as have herein been indicated. On the other hand, the diminution in the height of the spiraled ridges may be carried to the ultimate, when the medial portion a. of the dowel will be smooth and cylindrical. The article even so will be fundamentally unlike a bolt that is screw-threaded throughout a portion only of its shank, in that it will under the blows of a sledge rotate as it penetrates.

The dowel of Figs. VVII, otherwise that of Figs. III, differs in that throughout its medial portion a. the shank of the dowel is smooth and cylindrical. The diameter throughout this medial portion is preferably, however, not the minimum diameter of the threaded terminal portions, but is of a diameter intermediate in value between the maximum and minimum diameters of the terminal portions; it is of a diameter equal, substantially, to the pitch diameter of the threaded terminal portions. The threads or ridges upon the terminal portions, however, are carefully aligned, so that, as the dowel is driven home the ridges upon the basal end 17 of the dowel will enter precisely the grooves of the opening made by the ridged forward end a. The basal end of the dowel will then fill the space snugly and completely; there will be no further tearing of wood fibre with consequent loss of security; and no space will remain permitting ingress of moisture.

It will be perceived that the ridges of the end portions diminish in height and merge in the surface of medial portion a, and that this medial portion, being (as is preferred) of somewhat larger diameter than the minimum diameter of portion 0, there will be rearwardly and outwardly flaring surfaces from the grooves between the threads of portion 0 to the cylindrical surface of portion a. These flaring surfaces will as the dowel is driven spread the wood fibres and turn them in the direction of advance, with the effect that when the dowel is driven home there is in the medial portion a increased resistance to retraction.

Such interruption as is here described in the continuity or in the height of the thread upon the shank of the dowel has no such weakening effect upon security as might be supposed. The dowel of the Graham and Peirce patent named above may not by any means be withdrawn. In a particular test of such a dowel driven into oak, the dowel was subjected to drawing pull of increasing intensity, until under a strain of approximately 4500 pounds the tensile strength of the material was exceeded and the dowel was torn in two. A dowel of the structure of Figs. V-VII of this application but otherwise corresponding to the dowel of the test described was similarly driven and tested, and, under a strain slightly less than the limit of tensile strength, at 4100 pounds, the wood gave way and the dowel was drawn out. It will of course be understood that these tests were tests of comparative security. Opportunity was in neither case afforded for the dowel to rotate. If opportunity to rotate be afforded, the dowel of this invention may be withdrawn under a tension well within the limit of strength of the material.

In driving the dowel of this invention may be slowly sunk under relatively light blows of a sledge.

The head of the dowel affords a surface that, remaining exposed, may carry any desired indicium, as, for instance, the date of application, to afford check upon durability.

The spiral ridged configuration may be given to the dowel by twisting a pre-formed rod of polygonal cross-section; but, preferably, the dowel of the invention will be formed by rolling in known manner an appropriate rod or blank between reciprocating dies.

I claim as my invention:

1. A dowel adapted to be sunk into wood and the like, including a spindle-like body bearing at its ends spiraled ridges, the turn of the spiral being at uniform rate longitudinally of the body and of an inclination permissive of rotation of the dowel under longitudinally directed driving stress and under longitudinally directed drawing stress as well, the ridges at the two ends of the body being in alignment, and the ridges extending throughout the length of the basal end of the body, whereby as the dowel is driven home the ridges of the basal end will follow in and fill without deforming the opening formed by the leading end and the driven home dowel will remain responsive to drawing stress, the height of such ridges diminishing --from the ends toward the medial portion of the body of the dowel.

2. A dowel adapted to be sunk into wood and the like, including a shank that in a medial portion of its extent is smooth surfaced and cylindrical, and at its two ends is provided with threads of uniform turn and of a pitch permissive of rotation of the dowel under longitudinally directed driving stress, the threads upon the two ends being aligned, whereby as the dowel is driven home the ridges of the basal end will follow in the opening formed by the leading end.

3. A dowel adapted to be sunk into wood and the like, including a shank that in a medial portion of its extent is smooth surfaced and cylindrical, and at its ends is threaded, the diameter of the medial portion being substantially the pitch diameter of the threaded ends, the threads of the two ends being of uniform turn and of a pitch permissive of rotation of the dowel under longitudinally directed driving stress, the threads upon the two ends being aligned, whereby as the dowel is driven home the threads of the basal end will follow in the opening formed by the leading end.

4. A dowel adapted to be sunk into wood and the like, including a spindle-like body bearing at its ends spiraled ridges, the turn of the spiral being at uniform rate longitudinally of the body and of an inclination permissive of rotation of the dowel under longitudinally directed driving and drawing stresses, the ridges at the two ends of the body being in alignment, and the ridges extending throughout the length of the basal end of the body, whereby as the dowel is driven home the ridges of the basal end will follow in and fill the opening formed by the leading end, and the driven-home dowel will remain responsive to drawing stress, the height of such ridges diminishing from the basal end toward the lead- 15 ing end of the dowel.

the like, including a spindle-like body bearing at its ends spiraled ridges, which ridges extend throughout the length of the basal end of the body, the turn of the spiral being at uniform rate longitudinally of the body throughout the two ends and of an inclination permissive of rotation under longitudinally directed driving and drawing stresses, the ridges at the two ends being in alignment, whereby as the dowel is driven home the ridges of the basal end will follow in and fill the opening formed by the leadingtend, the overall diameter of the dowel in the medial portion of its extent being less than at the ends, whereby response to drawing stress is facilitated.

HARRY C. GRAHAM. 

